![[tokkee]](http://tokkee.org/images/avatar.png){kind=avatar}
diff --git a/src/utils_latency.c b/src/utils_latency.c
--- /dev/null
+++ b/src/utils_latency.c
@@ -0,0 +1,173 @@
+/**
+ * collectd - src/utils_latency.c
+ * Copyright (C) 2013 Florian Forster
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Authors:
+ * Florian Forster <ff at octo.it>
+ **/
+
+#include "collectd.h"
+#include "utils_latency.h"
+#include "common.h"
+
+#ifndef LATENCY_HISTOGRAM_SIZE
+# define LATENCY_HISTOGRAM_SIZE 1000
+#endif
+
+struct latency_counter_s
+{
+ cdtime_t start_time;
+
+ cdtime_t sum;
+ size_t num;
+
+ cdtime_t min;
+ cdtime_t max;
+
+ int histogram[LATENCY_HISTOGRAM_SIZE];
+};
+
+latency_counter_t *latency_counter_create () /* {{{ */
+{
+ latency_counter_t *lc;
+
+ lc = malloc (sizeof (*lc));
+ if (lc == NULL)
+ return (NULL);
+
+ latency_counter_reset (lc);
+ return (lc);
+} /* }}} latency_counter_t *latency_counter_create */
+
+void latency_counter_destroy (latency_counter_t *lc) /* {{{ */
+{
+ sfree (lc);
+} /* }}} void latency_counter_destroy */
+
+void latency_counter_add (latency_counter_t *lc, cdtime_t latency) /* {{{ */
+{
+ size_t latency_ms;
+
+ if ((lc == NULL) || (latency == 0))
+ return;
+
+ lc->sum += latency;
+ lc->num++;
+
+ if ((lc->min == 0) && (lc->max == 0))
+ lc->min = lc->max = latency;
+ if (lc->min > latency)
+ lc->min = latency;
+ if (lc->max < latency)
+ lc->max = latency;
+
+ /* A latency of _exactly_ 1.0 ms should be stored in the buffer 0, so
+ * subtract one from the cdtime_t value so that exactly 1.0 ms get sorted
+ * accordingly. */
+ latency_ms = (size_t) CDTIME_T_TO_MS (latency - 1);
+ if (latency_ms < STATIC_ARRAY_SIZE (lc->histogram))
+ lc->histogram[latency_ms]++;
+} /* }}} void latency_counter_add */
+
+void latency_counter_reset (latency_counter_t *lc) /* {{{ */
+{
+ if (lc == NULL)
+ return;
+
+ memset (lc, 0, sizeof (*lc));
+ lc->start_time = cdtime ();
+} /* }}} void latency_counter_reset */
+
+cdtime_t latency_counter_get_min (latency_counter_t *lc) /* {{{ */
+{
+ if (lc == NULL)
+ return (0);
+ return (lc->min);
+} /* }}} cdtime_t latency_counter_get_min */
+
+cdtime_t latency_counter_get_max (latency_counter_t *lc) /* {{{ */
+{
+ if (lc == NULL)
+ return (0);
+ return (lc->max);
+} /* }}} cdtime_t latency_counter_get_max */
+
+cdtime_t latency_counter_get_average (latency_counter_t *lc) /* {{{ */
+{
+ double average;
+
+ if (lc == NULL)
+ return (0);
+
+ average = CDTIME_T_TO_DOUBLE (lc->sum) / ((double) lc->num);
+ return (DOUBLE_TO_CDTIME_T (average));
+} /* }}} cdtime_t latency_counter_get_average */
+
+cdtime_t latency_counter_get_percentile (latency_counter_t *lc,
+ double percent)
+{
+ double percent_upper;
+ double percent_lower;
+ double ms_upper;
+ double ms_lower;
+ double ms_interpolated;
+ int sum;
+ size_t i;
+
+ if ((lc == NULL) || !((percent > 0.0) && (percent < 100.0)))
+ return (0);
+
+ /* Find index i so that at least "percent" events are within i+1 ms. */
+ percent_upper = 0.0;
+ percent_lower = 0.0;
+ sum = 0;
+ for (i = 0; i < LATENCY_HISTOGRAM_SIZE; i++)
+ {
+ percent_lower = percent_upper;
+ sum += lc->histogram[i];
+ if (sum == 0)
+ percent_upper = 0.0;
+ else
+ percent_upper = 100.0 * ((double) sum) / ((double) lc->num);
+
+ if (percent_upper >= percent)
+ break;
+ }
+
+ if (i >= LATENCY_HISTOGRAM_SIZE)
+ return (0);
+
+ assert (percent_upper >= percent);
+ assert (percent_lower < percent);
+
+ ms_upper = (double) (i + 1);
+ ms_lower = (double) i;
+ if (i == 0)
+ return (MS_TO_CDTIME_T (ms_upper));
+
+ ms_interpolated = (((percent_upper - percent) * ms_lower)
+ + ((percent - percent_lower) * ms_upper))
+ / (percent_upper - percent_lower);
+
+ return (MS_TO_CDTIME_T (ms_interpolated));
+} /* }}} cdtime_t latency_counter_get_percentile */
+
+/* vim: set sw=2 sts=2 et fdm=marker : */